(AP) -- The international space station crew's wake up call from Mission Control this morning was Louis Armstrong's "What a Wonderful World." Astronaut Scott Parazynski said he couldn't think of a "more beautiful way to begin the day."
The astronauts were readying for a second spacewalk Sunday, preparing to work on the outside of the new Harmony addition and inspect a couple areas of concern on the orbiting outpost.
At 6 a.m. Eastern Time, two astronauts left the shuttle to begin installing handrails and other equipment outside the school bus-sized, live-in compartment at the space station.
Three more spacewalks are planned before Discovery is due to return to earth in nine days.
Spacewalkers Parazynski and Daniel Tani plan to detach a nearly 35,000-pound space station girder so it can be relocated later in the mission.
Once the pair detaches the bolts and cables that hold the girder in place, astronauts inside the station plan to use a robotic arm to move the truss to a location where it can be temporarily parked.
Installation is set for Tuesday during the mission's third spacewalk.
Meanwhile, Tani is scheduled to inspect a rotary joint for the station's solar wings that is acting up and check for possible sharp edges on a rail for the robot arm.
NASA had to cut a spacewalk short during Endeavour's August mission after one of the astronauts noticed a quarter-inch-long rip in the thumb of his glove. Another glove was damaged during an earlier flight, and Mission Control said sharp edges on the rail may be to blame in both cases.
Tani later plans to help Parazynski install a fixture on Harmony that will allow the station's robotic arm to move the compartment from its current temporary location to its permanent home. The space station's crew will relocate Harmony after Discovery leaves in another week.
The European Space Agency's science laboratory, named Columbus, will hook onto Harmony as early as December. The Japanese Space Agency's lab - called Kibo or in English, Hope - will latch onto Harmony early next year.
Harmony also will function as a nerve center, providing air, electricity and water for the space station. It was launched with racks of computer and electronic equipment pre-installed. All this gear had to be locked down for the jarring rocket ride to orbit, leaving the astronauts to undo more than 700 bolts to free up the equipment.
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